Tomato Salsa

This low-cal staple pumps up the flavor of everything from chicken breasts to scrambled eggs. "It's jam-packed with antioxidants, including lycopene, which may reduce the risk of some cancers, and beta-carotene, which may help fight heart disease," says Joan Salge Blake, RD, an associate clinical professor of nutrition at Boston University.

Eat It Up: Beta-carotene and lycopene are more easily absorbed by the body when consumed with a bit of healthy fat, so add some chopped avocado to your salsa-topped chicken. Or add salsa to Low Sodium V8 for extra fiber.

Whole Wheat Pitas

Give your usual turkey sandwich a healthy upgrade by swapping the bread for a whole wheat pita pocket. If you put veggies in your sandwich, it's usually a few lettuce leaves and a slice of tomato or else the bread falls apart. "But with a pita, you can stuff it full of vegetables and still get a healthy dose of whole grains," says Dawn Jackson Blatner, RD, a FITNESS advisory board member and author of The Flexitarian Diet. Just be sure to check the ingredients list: "enriched wheat flour" means the pita is an imposter. Look for the words "whole wheat."

Eat It Up: Go Greek by filling your pita with feta, hummus, diced cucumbers and tomatoes, arugula, and black olives. Or put a Mexican spin on your sandwich by adding low-fat refried beans, salsa, avocado, and chopped romaine lettuce. Rather have a snack? Make pita chips. Cut a pita into triangles, drizzle with olive oil, add a pinch of salt, and bake in the oven at 400 degrees for 10 minutes, or until crispy.

Popcorn

"Because it's super-low in calories, popcorn is the perfect food for those times when you don't want to worry about portion size," says Sharon Richter, RD, a nutritionist in New York City. And it's loaded with fiber, which is crucial for staying slim. In fact, people who maintain a healthy weight consume an average of 33 percent more fiber daily than those who are overweight, according to research.

Eat It Up: Save calories (and money) by getting a basic air popper. One we like: Orville Redenbacher's Gourmet Hot Air Popper by Presto ($25, bedbathandbeyond.com). Pop the kernels with a bit of salt and toss with nuts and raisins for a tasty trail mix.

Kale

This potent leafy green tastes like a slightly sharper version of spinach. Kale is rich in an antioxidant called kaempferol, which Harvard research shows may help lower your chances of developing ovarian cancer by 40 percent. "It's also a great source of iron and folate — which can prevent birth defects — as well as calcium and magnesium, making it a terrific choice for anyone who doesn't eat dairy products," says Dave Grotto, RD, a FITNESS advisory board member and author of 101 Foods That Could Save Your Life.

Eat It Up: Chop the veggie into thin strips and saute in a teaspoon of olive oil with chopped onions and mushrooms for five to 10 minutes. Or buy frozen kale to toss into stir-fries, soups, or pasta sauces.

Oranges

Apples get all the glory, but oranges are the unsung heroes of fresh fruit, says Susan Kraus, RD, a clinical dietitian at Hackensack University Medical Center in New Jersey. "They're very low in calories and a good source of potassium, fiber, and folate," Kraus says. Not to mention that a large orange has a day's worth of immunity-boosting vitamin C.

Grass-Fed Beef

It has 90 fewer calories and 11 grams less fat per 3.75-ounce serving than corn-fed beef. Plus, "it contains three times more healthy omega-3 fatty acids, which reduce inflammation, improve brain health, and lower your risk of heart disease," Grotto says. Grass-fed beef is also high in conjugated linoleic acid, a type of polyunsaturated fat that some researchers think may increase weight loss.

Eat It Up: Look for meat labeled "100 percent grass-fed"; "organic" doesn't guarantee the cows didn't have grain. Make healthy fajitas: Grill a piece of sirloin or tenderloin, which is relatively low in fat, slice it thinly, and serve with grilled veggies, salsa, beans, and tortillas.

Vegetable Soup

More than 70 percent of us don't eat the recommended three to five servings of veggies a day. An easy way to help meet your quota? Two cups of vegetable soup, says Blake. Plus, people who have a bowl before lunch consume 20 percent fewer calories during the meal. The combo of the broth and fiber-rich vegetables increases feelings of fullness, studies show.

Eat It Up: Check the sodium content on canned soup — a healthy pick has 480 milligrams or less. Or make your own by sauteing 1 teaspoon olive oil, 1 small chopped onion, and 1 teaspoon each minced garlic, dried oregano, and dried basil in a pot, Blatner says. Add 2 cups frozen mixed veggies and 4 cups low-sodium vegetable broth, bring to a boil, and simmer for 15 minutes. Puree half of the soup for a thicker, richer taste and texture.

Plain Yogurt

"Yogurt contains the perfect ratio of carbohydrates, protein, and fat — the carbs give you instant energy, while the protein and fat are released more slowly, keeping you full longer," Kraus says. In a recent study, dieters who consumed three 6-ounce servings of yogurt a day lost 61 percent more body fat overall than those who didn't eat yogurt. The researchers believe that the calcium in dairy increases the activity of enzymes that break down fat cells. Look for yogurts that have at least 20 percent of the RDA.

Eat It Up: Mix plain yogurt with a teaspoon of cinnamon or top it with berries for an easy, low-sugar snack. Or use plain Greek yogurt for an extra protein boost in recipes that call for mayo or sour cream, like tuna salad, veggie dip, or salad dressings.

Mangoes

"Mangoes are loaded with polyphenols, which help to counteract the effects of chemicals in your body that can damage cells and increase the risk of cancer and heart disease," Blake says. Plus, the juicy fruit is a great source of fiber, potassium, and beta-carotene, which may help protect your eyesight and boost your immune system.

Eat It Up: Fresh mango can be a chore to peel and chop, so consider buying it frozen. Defrost in the microwave and eat, or add a few cubes to yogurt or oatmeal. You can even make your own sorbet: Puree 2 cups frozen mango, the juice from 4 limes, and 2 tablespoons honey in a blender until smooth. Top with a dollop of yogurt.

Hummus

This delicious chickpea spread is a Mediterranean staple. Olive oil, the second ingredient in hummus, is probably the reason for most of the health benefits. "It slows digestion, helping to stabilize blood sugar, which keeps your appetite in check," says Mary Flynn, PhD, RD, an assistant professor of medicine at Brown University. Chickpeas are also a good source of protein, fiber, and iron.

Eat It Up: Store-bought hummus is fine, but watch portion size, Richter says. A regular-size tub can contain eight or more servings. (Those containing vegetables, like eggplant or red pepper, are usually slightly lower in calories). Spread hummus on sandwiches or veggie burgers, or mix with lemon juice and drizzle over a salad.